1. Field of the Invention
This invention is related in general to the field of optical microscopy. In particular, it relates to a method and apparatus for diagnostic testing of biological tissue with an array scanning microscope.
2. Description of the Related Art
Changes in the cellular structure of tissue are used to detect pathologic conditions, to assess the progress of precancerous conditions, and to detect cancer. Glass slides of tissue specimens are used for analyses of various kinds. A tissue sample is removed from a patient and is typically sectioned and fixed to a slide for staining and microscopic examination by a pathologist. The morphology of the tissue (the visually perceptible structure and shape of features in the tissue) is analyzed to provide a qualitative assessment of its condition and to identify the presence of pathologic changes, such as may indicate progression towards a malignancy. For many decades, this visual procedure has been the diagnostic mainstay of pathology.
With the advent of computers and sophisticated digital imaging equipment, researchers have extended the realm of histopathology through the use of mechanized procedures for diagnostic and quantitative investigation. Automated imaging systems are becoming more and more popular to scan the slides and record the information for computer analysis, for storage as digital files for later viewing, and for sharing via communication systems, including computer networks and the Internet. Because of the variety of tissues and analyses performed on the slides, as well as the type of scans being used, different modalities of imaging may be preferable or required for different types of samples and/or scans.
For example, in the case of brightfield whole-slide scanning, a glass slide may be imaged using red, green and blue light (RGB), or using a greater number of narrow-band channels (so-called multispectral imaging), or using several depths within the specimen (so-called z-stack imaging). RGB and multispectral imaging may be combined with z-stack imaging. Brightfield and fluorescence may also be available in the same instrument as alternative forms of imaging. Thus, as instruments become more and more capable of performing scans using such different modalities, automation will require that the instrument be also capable of selecting the best parameters of operation for each slide being scanned.
A recent innovation in the field of light microscopy utilizes a miniaturized microscope array, also referred to herein as a multiple objective array microscope, or simply as an “array microscope.” As described in commonly owned International Application PCT/US02/08286, herein incorporated by reference, each miniaturized microscope includes a plurality of optical elements individually positioned with respect to a corresponding image plane and configured to image respective sections of the sample. The array microscope further includes a plurality of image sensors corresponding to respective optical elements and configured to capture image signals from respective portions of the sample.
In such an array microscope, a linear array of miniaturized microscopes is preferably provided with adjacent fields of view that span across a first dimension of the sample (also referred to herein as y direction), and the sample is translated past the fields of view across a second dimension (x direction) to image the entire sample. Because the diameter of each miniaturized microscope objective is larger than its field of view (having respective diameters of about 2 mm and 250 μm, for example), the individual microscopes of the imaging array are staggered so that their relatively smaller fields of view are offset over the second dimension (the direction of scanning) but aligned over the first dimension, as illustrated in FIG. 1. As a result of such staggered arrangement of the rows of miniaturized microscopes, the continuous strip covered by the linear scan of each optical system is substantially free of overlap with the continuous strips covered by adjacent optical systems. At each acquisition frame each miniaturized microscope projects image data for a small section of the sample object directly onto a detector and the individual frame data are then used to form an image of the entire sample object by hardware or software manipulation. Thus, the detector array provides an effectively continuous linear coverage along the first dimension which eliminates the need for mechanical translation of the microscope in that direction, providing a highly advantageous increase in imaging speed by permitting complete coverage of the sample surface with a single scanning pass along the second dimension. The details of implementation of such array microscopes are disclosed in copending U.S. Ser. No. 10/637,486.
This invention is directed at optimizing the quality of tissue images acquired with an automated imaging system that processes large numbers of slides sequentially for storage, transmission, computerized analysis, and visual inspection. Rather than manipulating the initial image obtained from a first scan to produce an improved image, or repeating a scan of the same slide under different imaging modalities after a review of the initial image, the invention is directed at using known information about the type of tissue being analyzed and the type of analysis being sought in order to optimize the imaging modalities during the first scan. The idea is to produce tissue images rapidly and sequentially that are nearly optimal for their intended use, so that their analysis (visual or computerized) can proceed directly without a need for repetitive scans.